DE102011078321A1 - Refrigeration unit with evaporation tray and auxiliary device for evaporation promotion - Google Patents

Abstract

A refrigeration appliance, in particular a household refrigerating appliance, has at least one storage chamber (3) which can be closed by a door (2), an evaporation tray (9) for evaporating condensate discharged from the storage chamber (3) and an auxiliary device (10, 12) which is replaced by a Control unit (13) is switchable to increase the evaporation rate in the evaporation tray (9). The control unit (13) is arranged to detect an opening of the door (2) and to control the operation of the auxiliary device (10, 12) based on the number and / or duration of detected door openings and / or in dependence on the ambient temperature (text) and or to take into account the time profile of the temperature (Tv) of an evaporator (4) in controlling the operation of the auxiliary device (10, 12).

Description

The present invention relates to a refrigeration appliance, in particular a household refrigeration appliance such as a refrigerator or freezer, with an evaporation tray for evaporation of condensate derived from a storage chamber of the device, and an auxiliary device which is switchable to the evaporation of the condensation water in the evaporation tray if necessary to promote.

With each opening a door of the refrigerator enters with the ambient humidity and moisture in the storage chamber of a refrigerator and there is reflected over time at the coldest point down, that is, depending on the design of the refrigerator, for example, directly to an evaporator or at one through the Evaporator cooled wall of the storage chamber. From there, the moisture must be removed so that it does not affect the heat exchange between the storage chamber and the evaporator and thus the efficiency of the refrigerator and / or so that drained from this coldest point water does not wet the refrigerated goods. It is therefore usually below this coldest place a gutter or shell provided in which the condensation can collect and from where it is passed through a passage in the heat-insulating wall of the refrigerator to an evaporation tray. The evaporation tray is located beyond the heat-insulating wall to release moisture evaporating from it freely to the environment. To promote the evaporation in the shell, it is conventionally mounted in a machine room of the refrigerator on a compressor to be heated by its waste heat.

Improvements in insulation and cooling in modern refrigeration appliances mean that the ratio of accumulating condensate to the waste heat available at the compressor is becoming increasingly unfavorable. However, if the condensation is faster than it can evaporate in the evaporation tray, it overflows, and the leaking water can damage the unit and its surroundings.

One way to replace the lack of waste heat from the compressor is to attach an electrical heater to the evaporation tray. However, it is obvious that the operation of such a heater, especially if it is not controlled on demand, affects the overall energy efficiency of the refrigerator and largely eliminates efficiency gains through improved isolation or improved refrigeration. Although it would be conceivable to attach a level sensor to the evaporation tray and to operate the heater only if it indicates the exceeding of a critical water level. However, such a level sensor must have a high degree of reliability, because if a fault of the level sensor is that an exceeding of the critical water level is not detected, overflowing the evaporation tray threatens with the resulting consequential damage. If, on the other hand, a malfunction of the level sensor leads to the fact that an exceeding of the critical water level is constantly detected, then the heating device runs non-stop, and energy is wasted uselessly. Since such a disturbance does not immediately manifest itself externally, it may be overlooked for a long time and cause considerable costs for the user. However, a level sensor with the reliability required for practice leads to not negligible and often dissuasive for the user costs in the device manufacturing.

Object of the present invention is therefore to provide an inexpensive and reliable solution with which sufficient evaporation of condensation can be ensured and at the same time a good energy efficiency of the refrigerator is maintained.

A refrigeration appliance is understood in particular to be a household refrigeration appliance, that is to say a refrigeration appliance which is used for household purposes or possibly also in the gastronomy sector, and in particular for storing food and / or drinks in household quantities at specific temperatures, such as, for example, a refrigerator, a freezer , a fridge freezer, a freezer or a wine storage cabinet.

The object is achieved by providing, in a refrigeration appliance, in particular a domestic refrigeration appliance, with at least one closable by a door storage chamber, an evaporation tray for evaporating from the storage chamber derived condensate and an auxiliary device which can be switched by a control unit to the evaporation rate in the evaporation tray to increase, the control unit is adapted to detect an opening of the door and to control the operation of the auxiliary device based on the number and / or duration of detected door openings.

The effectiveness of this solution is based on the fact that the air exchange between the storage chamber and the environment each time the door is an essential source for precipitation in the storage chamber knocking water and consequently also the amount of condensation to be evaporated closely related to the number and duration of the door openings ,

In order to improve the accuracy with which the operation of the auxiliary device can be adapted to the accumulating amount of condensation water, the control unit may be configured to control the operation of the auxiliary device further depending on the ambient temperature, since the amount of moisture, which together with a given volume of air from the environment enters the storage chamber, in general, increases sharply with the temperature of the air.

To detect the ambient temperature, the control unit may be connected to a suitable temperature sensor.

With comparable reliability cheaper techniques are feasible to estimate the ambient temperature on the basis of related variables. Thus, for example, if the refrigeration device comprises a compressor which is operated intermittently in a manner known per se, the control unit can be set up to estimate the ambient temperature on the basis of the duration of an operating phase of the compressor. The duration of an operating phase depends not only on the difference between the switch-on and switch-off temperature of the compressor, but also on the rate at which ambient heat penetrates into the storage chamber and delays its cooling during operation of the compressor. The higher the ambient temperature, the higher the rate, and accordingly, each operating phase lasts longer.

Refrigeration appliances are also known, in which the capacity of the compressor is variable and regulated to a value at which the compressor can run continuously or almost continuously while keeping the temperature of the storage chamber constant. The capacity of the compressor to equalize the flow of heat from the storage compartment environment depends on the ambient temperature, specifically the difference between the ambient temperature and the temperature of the storage chamber, so that the performance to which the compressor is subjected at one such refrigeration device is regulated, also allows a conclusion on the ambient temperature.

Also known per se are refrigerators, in which a storage chamber is equipped with a humidity sensor to detect the humidity in the storage chamber and to allow a controlled dehumidification of the air to a tuned to the refrigerated goods contained therein target value. The amount of condensate arising in such a controlled dehumidification can be accurately estimated on the basis of the measured humidity values and can be used to control the auxiliary device.

An indirect estimate of the humidity is possible even without a special humidity sensor. Thus, for example, a temperature sensor for detecting the temperature of the evaporator may be arranged on an evaporator cooling the storage chamber in order to detect the change in the evaporator temperature during startup. Moisture condensing on the evaporator delays its cooling, so that by comparing the time course of cooling with a normal course without condensation, the amount of condensation can be estimated, which is reflected in this in an operating phase of the evaporator on this.

If the average operating temperature of the evaporator is so low that atmospheric moisture precipitates on it as frost, which does not defrost between two operating phases of the evaporator, defrosting may be provided to defrost the evaporator. Liquid condensate essentially only accumulates when the defrost heater is in operation. Therefore, in such a case, the control unit is preferably arranged to operate this device together with the defrost heater in order to quickly eliminate this defrost water.

Conveniently, the consideration of the various above-mentioned, the amount of accumulating condensation water influencing variables take place by the control unit is set to change at each door open a count size by an increment based on at least one of door opening duration, ambient temperature, compressor runtime, compressor performance, humidity in the storage chamber and rate of change of the evaporator temperature selected size, and to operate the auxiliary device when the count size reaches a limit.

As an auxiliary device, in particular a heater and / or a fan come into consideration.

Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying figures. From this description and the figures also show features of the embodiments, which are not mentioned in the claims. Such features may also occur in combinations other than those specifically disclosed herein. Therefore, the fact that several such features are mentioned in the same sentence or in a different type of textual context does not justify the conclusion that they can occur only in the specific combination disclosed; instead, it is generally to be assumed that individual ones of several such features are also omitted or modified can, if this does not affect the functionality of the invention in question. Show it:

1 a schematic section in the width direction by a household refrigerator according to the present invention;

2 a section in the depth direction by the refrigerator;

3 a flowchart of a method for controlling the evaporation assisting auxiliary device;

4 a flowchart of one in the context of the control method of 3 applicable method for estimating the ambient temperature;

5 a flowchart of a method for estimating the ambient temperature, which is applicable in a refrigeration device with variable-capacity compressor;

6 exemplary temperature curves on the evaporator of the refrigerator 1 and 2 ; and

7 a flowchart of a method for controlling the auxiliary device, which on the in 6 shown temperature curves based; and

8th a flowchart of a second on the temperature curves of 6 based method.

1 and 2 show schematic sections through a household refrigerator, in which the present invention is applicable. The sectional planes of the two figures are shown in the other Fig. As dash-dotted lines II and II-II.

The household refrigerator, here a refrigerator, has in the usual way a heat-insulating housing with a body 1 and a door 2 holding a storage chamber 3 limit. The storage chamber 3 is here by one at its rear wall between an inner container of the corpus 1 and a coldwall evaporator disposed surrounding this insulating foam layer 4 cooled, but it should be readily apparent to those skilled in the art that the features of the invention explained below are also applicable in conjunction with any other types of evaporator.

The evaporator 4 is part of a chiller, which also has one in the body 1 recessed engine room 5 housed compressor 6 and comprises a condenser, not shown in the figures, for example, the outside of the rear wall of the body 1 or in the engine room 5 can be accommodated.

At the foot of the evaporator 4 cooled rear wall of the storage chamber 3 extends a gutter 7 for condensation, which is on the evaporator 4 chilled area of the inner container precipitates and flows down it. A pipeline 8th leads from the lowest point of the gutter 7 through the insulating foam layer to an evaporation tray 9 placed on a housing of the compressor 6 is mounted to by waste heat of the compressor 6 to be heated. An electric heater 10 is here in the form of an inside the evaporation tray 9 extending heating loop shown; It could also, for example, in the form of a film heater on an outer wall 11 the evaporation tray 9 be attached, in which case outside of the film heater still around an insulating layer may be provided to ensure that the heater their heat substantially in the evaporation tray 9 into it.

To the evaporation of condensation in the evaporation tray 9 to promote, in place of the heater 10 or in addition to this one more fan 12 in the engine room 5 be arranged so that it has a flow of air over the water level of the evaporation tray 9 drives. Since the on and off times of the heater 10 and the fan 12 linked together and preferably the same, the description may be limited to the case that both are present.

heater 10 and fan 12 are controlled by an electronic control unit 13 here for simplicity in the engine room 5 is shown, but in practice largely arbitrarily on the refrigerator and in particular adjacent to a - not shown here - control panel can be arranged. The control unit 13 also controls the operation of the compressor 6 on the basis of one at the storage chamber 3 arranged temperature sensor 14 , As will be explained in more detail below, in the context of the invention, a simple on-off control of the compressor 6 be provided at the control unit 13 the compressor 6 turns on when the temperature of the storage chamber 3 a switch-T _a exceeds and off it again once the temperature of the storage chamber 3 a switch-off threshold T _off below. However, there is also a continuous control of the power, in particular the speed of the compressor 6 or switching between numerous discrete non-vanishing power levels of the compressor 6 depending on the measured temperature.

On a side wall of the carcass 1 is a through the door 2 actuatable switch 15 attached, in a conventional manner for switching on and off a lamp 16 the storage chamber 3 when opening or closing the door 2 can serve. The desk 15 is with the control unit 13 connected to a detection of the opening and closing of the door 2 through the control unit 13 to enable.

For some of the control methods described below, a second temperature sensor 17 directly on the evaporator 4 be arranged to detect its temperature and to the control unit 13 Report to.

3 is a schematic flow diagram of a method according to a first embodiment of the invention in the control unit 13 is executable to the operation of the heater 10 and the fan 12 to control. In step S31, the control unit waits 13 that off the switch 15 an opening of the door 2 detected. If so, in step S32, an internal counter c of the control unit 13 increments by an increment incr, which may be a constant in a simple embodiment, which according to a preferred development, however, depends directly or indirectly on the temperature T _ext in the vicinity of the refrigerator and possibly also of other sizes. In order to be able to estimate the outside temperature T _ext , an ambient temperature _sensor can be provided on the refrigeration device outside the insulation layer. However, it is preferred to save the costs of such a sensor and to estimate the ambient temperature T _ext in an indirect way, as will be explained in more detail below.

Another size that can affect the increment is the length of time the door is open 2 , It is easy to understand that the amount of ambient air when opening the door 2 in the storage room 3 The longer the door, the larger it gets 2 is open, and that, accordingly, the amount of water introduced with the ambient air increases. As soon as the air in the storage room 3 is completely replaced, the registered amount of moisture increases only slowly. Therefore, it can be assumed in a simple embodiment of the method that with each door opening the air is completely replaced; then only the number of door openings, but not their duration in the increment needs to be considered. A more accurate estimate of the moisture input is achieved if a correspondingly reduced increment is taken as the basis for a short door open which is insufficient for complete air exchange.

If in the storage room 3 a humidity sensor is provided, its measured value after re-closing the door 2 be used to determine the amount of water vapor in storage chamber 3 to estimate quantitatively and to set the increment accordingly.

In step S33, it is checked whether the counter has exceeded a limit value c _{max which} corresponds to a critical water level in the evaporation tray 9 equivalent. If this is the case, in step S34, the heater 10 and / or the fan 12 turned on, the counter c is reset in step S35, and the process returns to the output. While heating device 10 and fan 12 In operation, the detection of door openings with the steps S31, S32, S33 and the concomitant renewed incrementation of the counter c continues. Each after a predetermined period of operation, which is empirically determined to be sufficient to evaporate an amount of water corresponding to the limit c _max and so the water level in the evaporation tray 9 to lower again to a safe level will be heating device 10 and fan 12 switched off again.

To the contribution of the waste heat of the compressor 6 for evaporation in the shell 9 In the case of an on-off control of the compressor can take into account 6 through the control unit 13 be provided that when the compressor 6 is in operation, the count c is reduced at regular intervals by a predetermined decrement. In the case that the compressor 6 is operated continuously at variable power, the amount of decrement can be set proportional or the time interval between two decrements inversely proportional to the compressor power.

4 illustrates a first method for indirect estimation of the outside temperature T _ext , which is applicable when the compressor 6 from the control unit 13 is controlled on-off. In step S41 it is waited until the temperature sensor 14 detected temperature T of the storage chamber 3 rises above the switch-T _one. Once this is the case, in step S42 the compressor 6 switched on and a timer started. In particular, the timer may count on clock periods of a clock of the control unit 13 based. Once it is determined in step S43 that the temperature of the storage chamber 3 has dropped to the switch-off _of T, the compressor is 6 again turned off, the timer is stopped and recorded since the step S42 elapsed time t, and the outdoor temperature T _ext is estimated based on a lookup table in which these as a function f of the (user adjustable) on threshold T _and the delay time t of the compressor 6 is recorded. The table that t the relationship between f T _a turn-on threshold, compressor run time and temperature T _ext environment describes is determined by the manufacturer of the refrigerator in advance empirically and in a read-only memory of the control unit 13 been filed.

An estimate of the outside temperature T _ext based on the measured compressor running time t is then possible in a particularly accurate manner when the door 2 during operation of the compressor 6 between steps S42 and S44, does not open. It can therefore be provided that the procedure of 4 terminates without result and a previous estimate of T _ext is used if during operation of the compressor 6 an opening of the door 2 is detected.

Since the difference between the input and switch-off thresholds T _a, T _out is generally fixed, is obvious that also the switch-off _of T or an average value between the two thresholds T _a, T _of for the estimation of T _ext could be used ,

5 shows the flowchart of a method for estimating the ambient temperature T _ext , which is applicable to a refrigerator whose compressor 6 switchable between different non-zero power levels. The procedure is repeated at regular intervals. In this method, an upper limit T _max and a lower limit T _min for the temperature of the storage chamber 3 which, if possible, should not be exceeded or fallen short of for a longer period of time. If in step S51 when comparing the temperature T of the storage chamber 3 with the upper limit T _{max is} determined that the temperature T of the storage chamber 3 is above the upper limit T _max , the power PV of the compressor is increased in step S52 6 increased by a predetermined increment ε.

The time interval between two repetitions of the method is chosen to be large enough to be able to observe an effect of the changed compressor power PV on the temperature T. If the compressor power PV after the increase is sufficient to lower the temperature T, and it is determined in step S51 that the temperature T has dropped below T _max , then the process branches from step S51 to S53 where the temperature T is equal to the temperature T lower limit T _{min is} compared. If this is not exceeded, the compressor power PV remains unchanged, and in turn begins after the predetermined time interval, the process again.

Finally, if the temperature T is less than T _min , the compressor power is reduced again by the value ε in step S54. In this way, the compressor power PV continuously adapts to the variable according to the ambient temperature T _ext variable cooling demand of the storage chamber 3 at. So always when the door 2 of the refrigerator is opened, in step S55, the ambient temperature T _ext as a function of the actual temperature T of the storage chamber 3 or their user-set limits T _max , T _min and the compressor power PV can be estimated using recourse to a table empirically determined by the refrigerator for the relevant model.

A method of controlling the operation of heater 10 and fan 12 , which determines the moisture input not via the detour of an estimate of the ambient temperature, but directly, is determined by the 6 and 7 explained. The diagram of 6 shows two curves of the temperature Tv of the evaporator 4 as a function of time t, it being assumed in each case that the control unit is at a time t0 13 the compressor 6 turns. Before the switch-on time t0, with the compressor switched off 6 , the temperature Tv of the evaporator rises 4 together with the temperature T of the storage chamber 3 very slowly. A short time after switching on the compressor 6 the temperature Tv starts to drop. The rate of temperature drop depends on the humidity in the storage chamber 3 or the rate at which this humidity on the evaporator 4 precipitated as condensation. The fastest drop, shown as curve A in 6 , then arises when the air in the storage chamber 3 is dry and no heat of condensation due to condensation on the evaporator 4 is released. However, when condensation is precipitated, this delays the cooling of the evaporator 4 , and it results in a curve such as the curve B. In practice, this means: if between two operating phases of the compressor 6 the door 2 not been opened and no humidity new to the storage chamber 3 has arrived, then a temperature profile according to curve A is expected; is the door 2 on the other hand, the curve B results, and the deviation between the two curves allows a conclusion to be drawn about the amount of condensate separated off at the evaporator.

That in the flowchart of 7 The illustrated method uses this variable cooling behavior of the evaporator 4 to the heater 10 and the fan 12 to control: in step S71 the control unit waits 13 from, until the temperature T of the storage chamber 3 has risen above the turn-T _one. Once this is the case, in step S72 the compressor 6 is turned on, and a timer is started to measure the elapsed time t from the turn-on time t0.

In step S73 it is decided whether since the last time the compressor is switched on 6 the door 2 has been open. If not, then it can be assumed that the air in the storage chamber 3 so dry is that the formation of frost on the evaporator 4 will be negligible in the now commencing phase of operation, and the method advances to step S74 to determine the evaporator temperatures measured during this phase of operation as reference temperatures Tv _ref (t) corresponding to curve A of FIG 6 save.

If, on the other hand, a door opening has taken place, then in step S75 the temperature sensor is used 17 the actual temperature Tv measured at the evaporator at the current time t and compared with the value Tv _ref (t) obtained in an earlier operating phase. The difference between the two temperatures Tv (t) and Tv _ref (t) is a measure of the rate at which condensate on the evaporator 4 reflected. A count c is incremented by this difference. In step S76, the count value c is compared with a threshold value c _max , and as with reference to FIG 3 described, are exceeded when the threshold c _max heater 10 and fan 12 is started (S77), and the count value c is reset (S78). The steps S75, S76 are repeated so long until it is determined in step S79 that the storage chamber to the switch-off temperature T _out is cooled. Once this is the case, the process returns to the origin S71.

The repeated summation in step S75 corresponds to a numerical integration of the difference between the two curves B, A of FIG 6 , The value of the integral, c, is proportional to the accumulated amount of condensation water. The period of time during the heater 10 and fan 12 remain switched on after step S77, is empirically determined so that it is sufficient to evaporate the c _max corresponding amount of condensation water. This period of time is obvious from the heater's power 10 and the fan 12 , but also from the waste heat performance of the in-service compressor 6 dependent.

8th shows a flowchart of a second based on the evaluation of the condensation heat based method. The steps of waiting for the on-temperature T to come on _, S81 and to turn on the compressor S82 and start the timer correspond to steps S71, S72. When the compressor has run for a first predetermined time t1, a first measurement of the evaporator temperature Tv (t1) takes place (S83). A second measurement (S84) takes place at time t2.

In step S85, it is decided whether since the last time the compressor is turned on 6 the door 2 has been open. If not, the measured values obtained in steps S83 and S84 are stored as reference values TV _ref (t1), TV _ref (t2) of the curve A (S86). If yes, then a typical rate of decrease of curve B can be determined from these two measurements. In step S87, the difference between this rate of decrease and that in an earlier phase of operation of the compressor 6 calculated decrease rate Tv _ref (t2) -Tv _ref (t1) of the curve A calculated at these two times. This difference is in turn representative of the condensation rate at the evaporator 4 and thus for the total amount of moisture in the air of the storage chamber 3 is included and over the course of the current operating phase of the compressor 6 on the evaporator 4 will knock down. Accordingly, the count c is incremented by this difference in S87. The value of c is thus representative of the amount of condensation water at the end of the operating phase of the compressor 6 the evaporation tray 9 would be included, unless the evaporation by operation of the heater 10 and the fan 12 is encouraged.

In step S88, it is checked whether the count value c has exceeded the threshold c _max . If not, the fan will be in the current operating phase of the compressor 12 and the heater 10 is not needed and the process returns to step S81 to await the next compressor operation phase. If c _{max is} exceeded, heater will be 10 and fan 12 is switched on (S89) and remains in operation as long as necessary in order to evaporate the amount of water corresponding to c _max .

Accordingly, the count value is decremented by c _max in step S90 before the process returns to step S81

Claims (12)

Refrigerating appliance, in particular household refrigerating appliance, with at least one through a door ( 2 ) lockable storage chamber ( 3 ), an evaporation tray ( 9 ) to evaporate from the storage chamber ( 3 ) and auxiliaries ( 10 . 12 ), controlled by a control unit ( 13 ) is switchable to the evaporation rate in the evaporation tray ( 9 ), characterized in that the control unit ( 13 ), opening the door ( 2 ) and the operation of the auxiliary equipment ( 10 . 12 ) based on the number and / or duration of detected door openings. Refrigerating appliance according to claim 1, characterized in that the control unit ( 13 ) is arranged to further control the operation of the auxiliary device in dependence on the ambient temperature (T _ext ). Refrigerating appliance according to claim 2, characterized by an ambient temperature sensor connected to the control unit. Refrigerating appliance according to claim 2, characterized in that it is operated intermittently Compressor ( 6 ) and that the control unit ( 13 ), the ambient temperature (T _ext ) based on the duration (t) of an operating phase of the compressor ( 6 ) (S42-S44). Refrigerating appliance according to claim 2, characterized in that it has a compressor ( 6 ) for holding the storage chamber ( 3 ) is operable at a target temperature with variable power, and that the control unit ( 13 ) is set, the ambient temperature based on the performance of the compressor ( 6 ) (S55). Refrigerating appliance according to one of the preceding claims, characterized in that it comprises a humidity sensor for detecting the humidity in the storage chamber and the control unit is adapted to take into account the measured humidity in controlling the operation of the auxiliary device. Refrigerating appliance according to one of the preceding claims, characterized in that it has an evaporator ( 4 ) for cooling the storage chamber ( 3 ) and one on the evaporator ( 4 ) for detecting the temperature (Tv) arranged temperature sensor ( 17 ) and that the control unit ( 13 ), the timing of the evaporator temperature (Tv) in controlling the operation of the auxiliary device ( 10 . 12 ) (S73-S75, S83-S87). Refrigerating appliance according to claim 7, characterized in that the control unit ( 13 ) is arranged to calculate the deviation of the time derivative of the evaporator temperature from a reference value (S85). Refrigerating appliance according to claim 7, characterized in that the control unit ( 13 ) is arranged to integrate the difference between a measured and an expected temperature of the evaporator (S73). Refrigerating appliance according to one of the preceding claims, characterized in that it has a defrost heater and that the control unit is adapted to operate the auxiliary device together with the defrost heater. Refrigeration appliance according to claim 1, characterized in that the control unit is arranged at each door opening a count size (c) to change an increment (S32), based on at least one of door opening duration, ambient temperature, compressor run time, compressor power, humidity in the storage chamber and rate of change the evaporator temperature selected size, and the auxiliary device ( 10 . 12 ) (S34) when the counted quantity (c) reaches a limit value (c _max ). Refrigerating appliance according to one of the preceding claims, characterized in that the auxiliary device is a heater ( 10 ) and / or a fan ( 12 ).

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